This invention relates to switched networks for radio signals, which are defined as those signals about 500 Kilohertz, and in particular, to Positive-Intrinsic-Negative (PIN) diode switched networks.
PIN diode switched networks such as antenna couplers, variable inductances, and variable capacitances have been hampered in the past by the adverse effects on the radio signal performance of the devices caused by the dc biasing circuitry necessary to control switching of the PIN diodes. An article appearing in the March/April 1979 issue of RF Design entitled, "Design with PIN diodes, Part I", by Gerald Hiller describes the prior art PIN diode application to HF, UHF and microwave circuits. The article was continued in Part II which appeared in the May/June 1979 issue of RF Design magazine and was entitled, "Design with PIN Diodes, Part II", by Gerald Hiller.
In August 1979 the Rome Air Development Center released a final technical report No. RADC-TR-79-210 entitled, "Electronically Tuned UHF Receiver Preselector" by Thomas Swanson. The article discusses in general the applications of PIN diodes as switching elements in UHF circuits, and in particular, UHF circuits such as preselector which essentially serve the same functions by being placed between the receiver and an antenna as an antenna coupler but providing selectivity to the receiver for removing unwanted signals. The article went into great detail evaluating the application of PIN diodes as a means of biasing the tuned circuits necessary to implement the tuning of the preselector.